According to a new study in the Journal of Neuroscience, a language-related gene known as FOXP2 — which is essential for speech in humans and for communication in mice — is more active in young girls than it is in young boys.

The paper was published Feb. 20. It suggests that there is a biological pathway underlying the observation that girls develop speech sooner than boys.

Measuring the amount of FOXP2 protein in the brain language areas of 4- and 5-year-old children who had recently died in accidents, the team found 30 percent more FOXP2 in girls than boys.

Interestingly, they found the exact opposite in the mice they studied — higher FOXP2 levels in boys. Language is a complicated phenomenon which most likely encompasses more than one gene, the authors warn, but this is the first sex difference they've seen in gene expression.